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Overview
Comment:Enhance the plan solver to take into account the number of output rows when computing the set of paths to retain for the next cycle.
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SHA1:1a46a7242313da96420985fa52e1de3f84533e5b
User & Date: drh 2013-09-06 17:45:42
Context
2013-09-07
00:29
Continuing refinements of the logic to take WHERE clause terms not used for indexing into account when computing the number of output rows from each table. check-in: b65dc534 user: drh tags: unlikely-func
2013-09-06
17:45
Enhance the plan solver to take into account the number of output rows when computing the set of paths to retain for the next cycle. check-in: 1a46a724 user: drh tags: unlikely-func
15:23
Initial implementation of the unlikely() SQL function used as a hint to the query planner. check-in: 036fc37a user: drh tags: unlikely-func
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/resolve.c.

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            pExpr->iTable = exprProbability(pList->a[1].pExpr);
            if( pExpr->iTable<0 ){
              sqlite3ErrorMsg(pParse, "second parameter to unlikely() must be "
                                      "between 0.0 and 1.0");
              pNC->nErr++;
            }
          }else{
            pExpr->iTable = 100;
          }             
        }
      }
#ifndef SQLITE_OMIT_AUTHORIZATION
      if( pDef ){
        auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0, pDef->zName, 0);
        if( auth!=SQLITE_OK ){







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            pExpr->iTable = exprProbability(pList->a[1].pExpr);
            if( pExpr->iTable<0 ){
              sqlite3ErrorMsg(pParse, "second parameter to unlikely() must be "
                                      "between 0.0 and 1.0");
              pNC->nErr++;
            }
          }else{
            pExpr->iTable = 75;
          }             
        }
      }
#ifndef SQLITE_OMIT_AUTHORIZATION
      if( pDef ){
        auth = sqlite3AuthCheck(pParse, SQLITE_FUNCTION, 0, pDef->zName, 0);
        if( auth!=SQLITE_OK ){

Changes to src/where.c.

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static int wherePathSolver(WhereInfo *pWInfo, WhereCost nRowEst){
  int mxChoice;             /* Maximum number of simultaneous paths tracked */
  int nLoop;                /* Number of terms in the join */
  Parse *pParse;            /* Parsing context */
  sqlite3 *db;              /* The database connection */
  int iLoop;                /* Loop counter over the terms of the join */
  int ii, jj;               /* Loop counters */

  WhereCost rCost;             /* Cost of a path */

  WhereCost mxCost = 0;        /* Maximum cost of a set of paths */

  WhereCost rSortCost;         /* Cost to do a sort */
  int nTo, nFrom;           /* Number of valid entries in aTo[] and aFrom[] */
  WherePath *aFrom;         /* All nFrom paths at the previous level */
  WherePath *aTo;           /* The nTo best paths at the current level */
  WherePath *pFrom;         /* An element of aFrom[] that we are working on */
  WherePath *pTo;           /* An element of aTo[] that we are working on */
  WhereLoop *pWLoop;        /* One of the WhereLoop objects */
  WhereLoop **pX;           /* Used to divy up the pSpace memory */
................................................................................
        u8 isOrdered = pFrom->isOrdered;
        if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
        if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
        /* At this point, pWLoop is a candidate to be the next loop. 
        ** Compute its cost */
        rCost = whereCostAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
        rCost = whereCostAdd(rCost, pFrom->rCost);

        maskNew = pFrom->maskLoop | pWLoop->maskSelf;
        if( !isOrderedValid ){
          switch( wherePathSatisfiesOrderBy(pWInfo,
                       pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
                       iLoop, pWLoop, &revMask) ){
            case 1:  /* Yes.  pFrom+pWLoop does satisfy the ORDER BY clause */
              isOrdered = 1;
................................................................................
              break;
          }
        }else{
          revMask = pFrom->revLoop;
        }
        /* Check to see if pWLoop should be added to the mxChoice best so far */
        for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){

          if( pTo->maskLoop==maskNew && pTo->isOrderedValid==isOrderedValid ){



            testcase( jj==nTo-1 );
            break;
          }
        }
        if( jj>=nTo ){
          if( nTo>=mxChoice && rCost>=mxCost ){


#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf("Skip   %s cost=%3d order=%c\n",
                  wherePathName(pFrom, iLoop, pWLoop), rCost,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            }
#endif
            continue;
          }
          /* Add a new Path to the aTo[] set */
          if( nTo<mxChoice ){
            /* Increase the size of the aTo set by one */
            jj = nTo++;
          }else{
            /* New path replaces the prior worst to keep count below mxChoice */
            for(jj=nTo-1; aTo[jj].rCost<mxCost; jj--){ assert(jj>0); }
          }
          pTo = &aTo[jj];
#ifdef WHERETRACE_ENABLED
          if( sqlite3WhereTrace&0x4 ){
            sqlite3DebugPrintf("New    %s cost=%-3d order=%c\n",
                wherePathName(pFrom, iLoop, pWLoop), rCost,
                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
          }
#endif
        }else{
          if( pTo->rCost<=rCost ){
#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf(
                  "Skip   %s cost=%-3d order=%c",
                  wherePathName(pFrom, iLoop, pWLoop), rCost,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
              sqlite3DebugPrintf("   vs %s cost=%-3d order=%c\n",
                  wherePathName(pTo, iLoop+1, 0), pTo->rCost,
                  pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
            }
#endif
            testcase( pTo->rCost==rCost );
            continue;
          }
          testcase( pTo->rCost==rCost+1 );
          /* A new and better score for a previously created equivalent path */
#ifdef WHERETRACE_ENABLED
          if( sqlite3WhereTrace&0x4 ){
            sqlite3DebugPrintf(
                "Update %s cost=%-3d order=%c",
                wherePathName(pFrom, iLoop, pWLoop), rCost,
                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            sqlite3DebugPrintf("  was %s cost=%-3d order=%c\n",
                wherePathName(pTo, iLoop+1, 0), pTo->rCost,
                pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
          }
#endif
        }
        /* pWLoop is a winner.  Add it to the set of best so far */
        pTo->maskLoop = pFrom->maskLoop | pWLoop->maskSelf;
        pTo->revLoop = revMask;
        pTo->nRow = pFrom->nRow + pWLoop->nOut;
        pTo->rCost = rCost;
        pTo->isOrderedValid = isOrderedValid;
        pTo->isOrdered = isOrdered;
        memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
        pTo->aLoop[iLoop] = pWLoop;
        if( nTo>=mxChoice ){

          mxCost = aTo[0].rCost;

          for(jj=1, pTo=&aTo[1]; jj<mxChoice; jj++, pTo++){

            if( pTo->rCost>mxCost ) mxCost = pTo->rCost;



          }
        }
      }
    }

#ifdef WHERETRACE_ENABLED
    if( sqlite3WhereTrace>=2 ){
................................................................................
    sqlite3ErrorMsg(pParse, "no query solution");
    sqlite3DbFree(db, pSpace);
    return SQLITE_ERROR;
  }
  
  /* Find the lowest cost path.  pFrom will be left pointing to that path */
  pFrom = aFrom;
  assert( nFrom==1 );
#if 0 /* The following is needed if nFrom is ever more than 1 */
  for(ii=1; ii<nFrom; ii++){
    if( pFrom->rCost>aFrom[ii].rCost ) pFrom = &aFrom[ii];
  }
#endif
  assert( pWInfo->nLevel==nLoop );
  /* Load the lowest cost path into pWInfo */
  for(iLoop=0; iLoop<nLoop; iLoop++){
    WhereLevel *pLevel = pWInfo->a + iLoop;
    pLevel->pWLoop = pWLoop = pFrom->aLoop[iLoop];
    pLevel->iFrom = pWLoop->iTab;
    pLevel->iTabCur = pWInfo->pTabList->a[pLevel->iFrom].iCursor;







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static int wherePathSolver(WhereInfo *pWInfo, WhereCost nRowEst){
  int mxChoice;             /* Maximum number of simultaneous paths tracked */
  int nLoop;                /* Number of terms in the join */
  Parse *pParse;            /* Parsing context */
  sqlite3 *db;              /* The database connection */
  int iLoop;                /* Loop counter over the terms of the join */
  int ii, jj;               /* Loop counters */
  int mxI = 0;              /* Index of next entry to replace */
  WhereCost rCost;          /* Cost of a path */
  WhereCost nOut;           /* Number of outputs */
  WhereCost mxCost = 0;     /* Maximum cost of a set of paths */
  WhereCost mxOut = 0;      /* Maximum nOut value on the set of paths */
  WhereCost rSortCost;      /* Cost to do a sort */
  int nTo, nFrom;           /* Number of valid entries in aTo[] and aFrom[] */
  WherePath *aFrom;         /* All nFrom paths at the previous level */
  WherePath *aTo;           /* The nTo best paths at the current level */
  WherePath *pFrom;         /* An element of aFrom[] that we are working on */
  WherePath *pTo;           /* An element of aTo[] that we are working on */
  WhereLoop *pWLoop;        /* One of the WhereLoop objects */
  WhereLoop **pX;           /* Used to divy up the pSpace memory */
................................................................................
        u8 isOrdered = pFrom->isOrdered;
        if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
        if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
        /* At this point, pWLoop is a candidate to be the next loop. 
        ** Compute its cost */
        rCost = whereCostAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
        rCost = whereCostAdd(rCost, pFrom->rCost);
        nOut = pFrom->nRow + pWLoop->nOut;
        maskNew = pFrom->maskLoop | pWLoop->maskSelf;
        if( !isOrderedValid ){
          switch( wherePathSatisfiesOrderBy(pWInfo,
                       pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
                       iLoop, pWLoop, &revMask) ){
            case 1:  /* Yes.  pFrom+pWLoop does satisfy the ORDER BY clause */
              isOrdered = 1;
................................................................................
              break;
          }
        }else{
          revMask = pFrom->revLoop;
        }
        /* Check to see if pWLoop should be added to the mxChoice best so far */
        for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){
          if( pTo->maskLoop==maskNew
           && pTo->isOrderedValid==isOrderedValid
           && ((pTo->rCost<=rCost && pTo->nRow<=nOut) ||
                (pTo->rCost>=rCost && pTo->nRow>=nOut))
          ){
            testcase( jj==nTo-1 );
            break;
          }
        }
        if( jj>=nTo ){
          if( nTo>=mxChoice 
           && (rCost>mxCost || (rCost==mxCost && nOut>=mxOut))
          ){
#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf("Skip   %s cost=%-3d,%3d order=%c\n",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            }
#endif
            continue;
          }
          /* Add a new Path to the aTo[] set */
          if( nTo<mxChoice ){
            /* Increase the size of the aTo set by one */
            jj = nTo++;
          }else{
            /* New path replaces the prior worst to keep count below mxChoice */
            jj = mxI;
          }
          pTo = &aTo[jj];
#ifdef WHERETRACE_ENABLED
          if( sqlite3WhereTrace&0x4 ){
            sqlite3DebugPrintf("New    %s cost=%-3d,%3d order=%c\n",
                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
          }
#endif
        }else{
          if( pTo->rCost<=rCost && pTo->nRow<=nOut ){
#ifdef WHERETRACE_ENABLED
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf(
                  "Skip   %s cost=%-3d,%3d order=%c",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
              sqlite3DebugPrintf("   vs %s cost=%-3d,%d order=%c\n",
                  wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
                  pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
            }
#endif
            testcase( pTo->rCost==rCost );
            continue;
          }
          testcase( pTo->rCost==rCost+1 );
          /* A new and better score for a previously created equivalent path */
#ifdef WHERETRACE_ENABLED
          if( sqlite3WhereTrace&0x4 ){
            sqlite3DebugPrintf(
                "Update %s cost=%-3d,%3d order=%c",
                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
            sqlite3DebugPrintf("  was %s cost=%-3d,%3d order=%c\n",
                wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
                pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
          }
#endif
        }
        /* pWLoop is a winner.  Add it to the set of best so far */
        pTo->maskLoop = pFrom->maskLoop | pWLoop->maskSelf;
        pTo->revLoop = revMask;
        pTo->nRow = nOut;
        pTo->rCost = rCost;
        pTo->isOrderedValid = isOrderedValid;
        pTo->isOrdered = isOrdered;
        memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
        pTo->aLoop[iLoop] = pWLoop;
        if( nTo>=mxChoice ){
          mxI = 0;
          mxCost = aTo[0].rCost;
          mxOut = aTo[0].nRow;
          for(jj=1, pTo=&aTo[1]; jj<mxChoice; jj++, pTo++){
            if( pTo->rCost>mxCost || (pTo->rCost==mxCost && pTo->nRow>mxOut) ){
              mxCost = pTo->rCost;
              mxOut = pTo->nRow;
              mxI = jj;
            }
          }
        }
      }
    }

#ifdef WHERETRACE_ENABLED
    if( sqlite3WhereTrace>=2 ){
................................................................................
    sqlite3ErrorMsg(pParse, "no query solution");
    sqlite3DbFree(db, pSpace);
    return SQLITE_ERROR;
  }
  
  /* Find the lowest cost path.  pFrom will be left pointing to that path */
  pFrom = aFrom;


  for(ii=1; ii<nFrom; ii++){
    if( pFrom->rCost>aFrom[ii].rCost ) pFrom = &aFrom[ii];
  }

  assert( pWInfo->nLevel==nLoop );
  /* Load the lowest cost path into pWInfo */
  for(iLoop=0; iLoop<nLoop; iLoop++){
    WhereLevel *pLevel = pWInfo->a + iLoop;
    pLevel->pWLoop = pWLoop = pFrom->aLoop[iLoop];
    pLevel->iFrom = pWLoop->iTab;
    pLevel->iTabCur = pWInfo->pTabList->a[pLevel->iFrom].iCursor;